The annual land-based reproductive and molting behavior of the Northern elephant seal as well as its exceptional diving behavior are widely recognized as an exceptional opportunity for the study of the physiological and biochemical events underlying these unusual abilities in a free-living mammal under natural conditions. Among the more unusual features of this annual 'amphibious' phenomenon is that with the exception of nursing pups all individuals fast entirely for 1-3 months while on land. In addition, while at sea all elephant seals dive continuously for from 3 to 7 months spending more than 90% of the time underwater at depths averaging 400m and occasionally in excess of 1000m. The research conducted over the last 20 years, sponsored by MBRS, other institutes of the HIH, NSF and other agencies, has provided a wealth of basic biological as well as medically relevant data. Of particular importance is an appreciation of some of the mechanisms which allow elephant seals to maintain physiological homeostasis during these natural fasts in stark contrast to the severe pathologies observed in other mammals including humans as a consequence of starvation or early childhood malnutrition or starvation which today reached global, epidemic proportion as well as clinically related conditions such as diabetes, kidney disorders, severe burns, and HPNS High Pressure Nervous Syndrome.